The present invention relates to a breather system for a two-cycle engine for adjusting the air pressure in a balancer gear chamber.
Some types of a two-cycle engine have a balancer chamber for housing gears and balancers. The balancer chamber is sealed with a sealing means and has an oil reservoir formed therein The oil in the oil reservoir is scooped up by balancer gears provided in the balancer chamber to lubricate the gears and bearings.
When the temperature of the engine rises after starting the engine or when the temperature drops after stopping the engine, the inner pressure in the balancer chamber varies. The pressure variation affects the sealing of the balancer chamber. To prevent the reduction of the sealing effect, a breather device is provided for adjusting the inner pressure.
Japanese Utility Model Publication 60-27765 discloses a breather system in which a breather chamber is formed on an upper portion of a balancer chamber The breather chamber is provided with a fine drill hole to communicate the breather chamber with the atmosphere through a tapped hole of a bolt provided for engaging a crankcase and a cylinder block. When the air in the balancer chamber expands and flows into the breather chamber, the oil included in the air is almost separated from the air in the breather chamber. Thereafter, the air passes through the drill hole where the oil is further separated from the air and the air discharges into the atmosphere through the tapped hole.
However, in the system, the air flowing into the breather chamber includes a large amount of oil. Therefore, it is necessary to provide a breather chamber having a large capacity to separate the oil from the air. Further, the manufacturing cost of the device increases because of forming a fine drill hole.